So-called tinned tube heat exchangers are widely used in a variety of applications in the fields of air conditioning, refrigeration and the like. Typically, such heat exchangers are comprised of plural rows of tubes in which a first heat transfer fluid, such as water, oil, air or a vapor compression refrigerant, flows while a second heat transfer fluid, such as air, is directed across the outside of the tubes. To improve heat transfer, a plurality of fins comprising thin sheets of metal are placed on the tubes. Each fin has multiple holes through which the tubes pass generally at right angles to the fins. The fins are arranged in parallel, closely spaced relationship along the tubes to form multiple paths for the second heat transfer fluid to flow across the fins and around the tubes.
One type of tinned tube heat exchanger is the so-called A-coil heat exchanger, which is comprised of two coil slabs coupled at their respective upper ends and diverging downwardly therefrom to define a generally "A" shape. Each slab typically has plural rows of heat transfer fluid carrying tubes in parallel array and plural fins through which the tubes are laced. The fins define inner and outer sides of each slab and a plurality of airflow passages between the corresponding inner and outer sides. The inner sides of the respective slabs are in generally facing relationship. The top, front and back of the heat exchanger are closed so that air to be cooled is constrained to flow outwardly through the slabs. Such A-coil heat exchangers are typically used as indoor heat exchangers and may be mounted above or below a furnace housing. The respective lower ends of the coil slabs are adapted to be received within a pan for collecting condensate drainage from the heat exchanger. The pan typically has a central opening positionable in registration with the closed top of the heat exchanger. Air to be cooled flows through the central opening into a region of the heat exchanger between the slabs and then outwardly through the slabs. The pan has a continuous channel for collecting condensate drainage from the heat exchanger. The channel should have sufficient width (along a minor dimension thereof) to accommodate the lower ends of the respective coil slabs. The greater the thickness of the slab (as measured between the inner and outer sides of the slab) the greater the width of the channel that is required to accommodate the lower end of the slab. Generally, the thickness of each slab is a function of the number of tube rows on the slab. The size of the drain pan usually depends on the width of the furnace housing with which the heat exchanger is mounted. For a given sized drain pan, the greater the width of the condensate collecting channel, the smaller will be the central opening in the drain pan.